MCB 2000 Exam 5 UCONN

Oligosaccharides

contain two or more monosaccharides linked by glycosidic bonds

disaccharides

two monosaccharides joined by glycosidic bond

polysaccharides

are many monomers in length (large polymeric oligosaccharides)

Glycosyltransferase

catalyze the formation of glycosidic bonds

How are the monosaccharide substrates for glycosyltransferases activated by

attachment to UDP (requires ATP)

Homopolymer

if all the monosaccharides in a polysaccharide are the same

storage form of glucose in animal cells

homopolymer and polysaccharide

how are glucose units in glycogen linked by

alpha-1,4-glycosidic bonds with an alpha-1,6-glycosidic bond every 12 subunits

how is glucose stored in plants

starch

forms of starch in plants

amylose and amylopectin

amylose

a linear polymer of glucose units linked by alpha-1,4-glycosidic bond

amylopectin

branched polymer with alpha-1,6-glycosidic bond every 30 alpha-1,4-glycosidic bond

cellulose

a homopolymer of glucose units linked by beta-1,4-glycosidic bonds (forms fibrils)

what do the alpha linkages of starch and glycogen form

compact hollow cylinders suitable for accessible storage

benefits of glucose stored as glycogen

immediate energy source without need to break down larger molecules, no energy cost, highly soluble

downsides of glucose stored as glycogen

the osmotic pressure of storing it leads to cell swelling and lysis

how does storing glucose as glycogen help

glycogen polymerizes 10k-55k glucose in to a single molecule which reduces osmotic particles

What makes the Ser-114 residues on glycogen phosphorylase A different from glycogen phosphorylase B?

A has phosphorylated Ser-114 residues (B phosphorylates its residues in order to convert to A)

Phosphorylase kinase

activator of Glycogen phosphorylase A, fully active when phosphorylated and bound to Calcium

Calmodulin

delta subunit of Phosphorylase kinase that senses calcium

Onset of fatigue

correlated to glycogen depletion but not an actual cause

Glucagon and epinephrine stimulate/inhibit ?

stimulates glucagon breakdown and inhibits glucagon synthesis

How many Glycogen Phosphorylase A is there for every one PP1 in the Insulin regulation pathway?

10 per PP1 as most of Phosphorylase A is converted in to B before PP1 dephosphorylates Glycogen Synthase B in to A to activate it

Diabetes

presence of excess glucose and underutilization of glucose, glucose is excreted in to urine

Difference between Type I and II Diabetes

Type I insulin is not produced and Type II Insulin is produced but the insulin signaling pathway isn’t responsive (insulin resistant)

How and where are fatty acids stored

in adipose tissue as TAGs liked to glycerol with ester linkages

where is adipose tissue located

below the skin (subcutaneous) and visceral (around the internal organs

Ways fatty acids act as TAGs

1.) breakdown of TAG to release fatty acids and glycerol in to the blood for tissues that require energy

2.) fatty acids are activated in the tissue and go in to the mitochondria for beta-oxidation

3.) activated fatty acids are broken down in to Acetyl Coa for the TCA cycle

what sends the signal for TAGs to be converted in to free fatty acids

epinephrine and glucagon

Ketogenic diets

are rich in fat and low in carbohydrates with good amount of protein so it can form ketone bodies

how are ketogenic diets used

reduce seizures in children that are afflicted with drug-epilepsy

What’s wrong with acetyl coa derived from fats

can’t lead to the synthesis of oxaloacetate or glucose because it can’t be converted due to the two carbon loss

diabetic ketosis

overproduction of ketone bodies when diabetes is untreated leading to acidosis

fatty acid release from adipose tissues is ____ in the absence of insulin function

enhanced